Aqueous pigment dispersion and process for producing the same

Abstract

It is provided an aqueous pigment dispersion having improved dispersing stability in which carbon black shows appropriate initial dispersing property and long-term dispersing property to water, and carbon black particles are less susceptible to aggregation. Moreover, it is provided a raw material for ink-jet ink having improved printing density when alkali metal cation is substituted by potassium ion. The present invention is summarized as an aqueous pigment dispersion, which contains surface modified carbon black that is obtained by wet-oxidizing carbon black by using hypohalous acid and/or a salt thereof, and alkali metal cation, characterized in that concentration of the alkali metal cation is not more than 2% by weight.

What is claimed is:  
     
       1. A preparation method of an aqueous pigment dispersion comprising the steps of: 
       finely dispersing carbon black into water;  
       oxidizing the carbon black by using hypohalous acid and/or an alkali metal salt thereof;  
       substituting a part of or the whole of alkali metal cation in the disperation by potassium ion; and  
       adjusting concentration of potassium ion in the dispersion to not more than 2% by weight.